Low-power crystal oscillator circuits are commonly used on digital integrated circuits to generate relatively low frequency digital clock signals. Typically the gain stage of the oscillator circuit is disposed on the integrated circuit whereas the crystal of the oscillator circuit is external to the package containing the integrated circuit.
FIG. 1 (Prior Art) is a circuit diagram of a low-power crystal oscillator circuit called a Pierce oscillator. Pierce oscillator 1 of integrated circuit 2 includes an inverting gain stage 3, a first resistor 4, a second resistor 5, a stray capacitance 6 and two terminals 7 and 8. The dashed line 9 indicates the boundary of the integrated circuit 2. A crystal 10 and two discrete capacitors 11 and 12 external to the integrated circuit are connected to terminals 7 and 8 in a pi configuration. The ability of the oscillator circuit to startup is dependent upon the magnitude of the stray capacitance 6. Moisture, terminal placement, package type and socket type affect the magnitude of the stray capacitance and therefore tend to make the oscillator circuit unreliable.